1. Field of the Invention
Methods consistent with the present invention relate to assembling a connector with an optical fiber that has air gaps or voids in its cladding, and more particularly to, heating the end of a bend-optimized fiber that has nanometer-scale air pockets infused in the cladding to close the air pockets before assembling the fiber in the connector.
2. Description of the Related Art
Bend-optimized optical fibers include a core that is surrounded by a cladding. A mesh of nanometer-scale air pockets is infused in the cladding to serve as a barrier that guides light back into the core when the fiber is bent with a very small bending radius, such as 1 cm. Bend-optimized optical fibers solve historic technical challenges related to installing fiber-to-the-home (FTTH) networks in high-rise apartment buildings and condominium complexes. Bend-optimized optical fibers prevent signal loss when bent around corners and routed through a building, enabling telecommunications carriers to install optical fiber cable into these complex environments and provide their customers with the near-infinite bandwidth benefits of a true FTTH solution.
Sections of bend-optimized fiber can be terminated on the ends with connectors, to allow regular connecting and disconnecting to an optical device or patching through adapters, that may be housed on modules, panels or shelves. Common types of connectors include SC, LC and ST connectors. FIG. 1 shows the typical components of a 3 mm and 900 μm SC connector. FIG. 2 shows the typical components of a 1.6/2.0 mm and 900 μm LC connector. FIG. 3 shows the typical components of a 3 mm and 900 μm ST connector.
Next, conventional methods of assembling 900 μm buffered Fiber, 3 mm (ST and SC only) and 1.6 mm or 2.0 mm (LC only) cable with Strength Member to connectors will be described with reference to FIGS. 4-11. However, other known methods of assembly may be used.
For 900 μm: Slide the small rubber boot onto the fiber. For 1.6/2.0/3.0 mm: Slide the strain relief boot and crimp sleeve onto the cable.
For 1.6/2.0/3.0 mm: Strip the cable jacket using a jacket stripper. Cut Kevlar with scissors. See FIGS. 4A, 4B and 4C.
Then remove the buffer from the fiber using a fiber strip tool, exposing the bare fiber. FIGS. 4A, 4B and 4C.
Clean the stripped fiber by drawing it through a cloth wipe soaked with fiber prep fluid. Sometimes the fiber may be primed by dipping and spraying the fiber and buffer with an adhesive primer. Common adhesives used for factory assembly of connectors include Epotek 353ND and Tracon F123. Common adhesive used for field assembly of connector includes Loctite 680. Place a needle on the nozzle of an adhesive bottle, such as Loctite 680.
Referring to FIGS. 5A, 5B and 5C, insert the needle into the ferrule stem until it bottoms against the base of the ceramic. Inject the adhesive into the ferrule until a bead of adhesive is seen at the front end of the ferrule. At this time, the ceramic ferrule should be filled half full with adhesive. Stop the adhesive injection process and remove the needle. Note that the adhesive should not be in the stem of the connector.
Next, referring to FIGS. 6A, 6B and 6C, carefully insert the fiber into the ferrule, pushing the 900 μm buffer into the connector until it stops (a slight rotation of the connector helps to feed the fiber through). The fiber should be protruding from the front of the ceramic ferrule.
Referring to FIGS. 7A, 7B and 7C, use a scribe tool to remove excess fiber by lightly scoring the fiber where it protrudes from the ceramic ferrule. To remove the excess, gently pull on the fiber.
Referring to FIGS. 8A, 8B and 8C, for 1.6/2.0/3.0 mm: Flare Kevlar out around the rear of the connector. Slide the crimp sleeves forward, capturing the Kevlar between the sleeve and the connector.
Referring to FIGS. 9A, 9B and 9C, for LC Only: Crimp the sleeve over the connector back shell. Using a heat gun, shrink the crimp sleeve tubing to fit the cable jacket. For SC & ST Only: Crimp the sleeve using the 0.178″ die over the connector back shell, and the 0.151″ die to crimp over the cable jacket. At this stage, if the assembly is made with a heat curing adhesive, such as Epotek 353ND or Tracon F123, the connector would have to be cured in an heat over, before shrinking the heat shrinks.
Then, for 900 μm: Push the boot up onto the rear of the connector. For 1.6/2.0/3.0 mm: Push the strain relief over the crimp sleeve and the cable jacket.
Next, use a cloth wipe (with fiber prep fluid) to dust off the surface of the rubber disc and metal polishing tool. Holding the 3 μm diamond film in one hand and the connector in the other, gently sand the fiber stub and any adhesive from the face of the ceramic ferrule. Clean the connector end face using a cloth wipe (with fiber prep fluid). Position the connector assembly in the metal polishing tool.
Referring to FIGS. 10A, 10B and 10C, place a piece of 3 μm AL203 film on the rubber pad (a small amount of water on the rubber pad will keep film in place). Add several drops of water on the film surface. Using a slow figure-8 motion, polish the end face for about 10 cycles.
Then, remove the 3 μm AL203 film from the rubber pad and wipe the connector again with a cloth wipe. Repeat the previous polishing step using 1 μm AL203 film.
Next, inspection of the fiber is recommended using a 100× microscope between steps to insure the fiber is not damaged. The entire fiber end-face should be visible without any cracks or significant scratches.
For SC only: After polishing, slide the SC coupling housing over the polished assembly until it latches.
Finally, referring to FIGS. 11A, 11B and 11C, place a dust cover on the connector until ready to use. Installation is now complete.
As described above, the polishing steps may include both dry and wet polishing processes. This can create a problem for fibers with air pockets because the nanometer-scale pockets infused in the cladding may trap debris from polishing films or fluids. If debris is trapped in the fiber, the optical performance of the fiber may be degraded. In addition, if debris stays in the fiber for a long period of time, the mechanical performance of the fiber may also degrade.
It is therefore an objective of this invention to assemble a connector with fibers with air pockets, such as bend optimized fibers, that prevents debris from being trapped in the fiber.